On 06/27/2017 10:59 AM, Gene Heskett wrote:
Greetings all;
I've not noted any great amount of mention of nurbs on the list, and I am
wondering how usable it is in doing something like a barrel taper
at "different" contours.
I am thinking in terms of a 6.5 Creedmoor, in 30" SS, which I can't get
any slimmer than whats called a medium Palma contour, which will likely
put old meat in the pot north of 15 lbs since its 13 and change with a
26" sporter weight barrel in it now.
What I'd like to do is put the last 20" of it on a diet to see if I can
get the weight, and balance back to what I've been used to since the
middle '60's.
What I have in mind is a 5 or 6 point curve that I can compose to look
like what I want, but about 6" long, then scale it in the Z axis to fit
the length by extending each anchor point by a scale factor multiplied
by that points position on the short modeling plot. I am assuming that
stretching the z with a fixed scale, will not distort the x shape to a
noticeable degree?
Secondarily, since facing it off against the side of a diamond wheel will
destroy the factory satin finish, how is the best way to restore that
when I've reached the size & weight goals?
Thanks for any hints, particularly about shapes that will reduce the
muzzle whipping on discharge since thats the vertical stringing on the
target, given that its vertical, since bedding errors can throw it in
any direction.
Many thanks for answers from the experts here.
Cheers, Gene Heskett
Gene,
Try fitting the curved part to a 2nd order polynomial. Stick some points
out there, modify until the
the curve looks right, then fit. A small program can then output gcode
as z vs x with whatever point
spacing you want.
Polish: cover the bed of your lathe with a oiled cloth to catch the grit
and polish between centers until
you get the surface finish you want. Cleanup the last bit with the next
finer grit by hand and parallel
to the bore. I usually finish up with well worn 320 grit but you can
polish to your hearts content.
You could even swamp it if you wanted to. ;-)
Hint: excel ...however I'm certain there is something already compiled
that will do the job.
Dave
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